Detail view showing method of operation of flush toilet. A toilet is a sanitation fixture used for the storing or disposal of human urine and feces. In developed countries, different forms of porcelain flush toilets are common: seats are used in the West while squat toilets are common in East Asia. These are connected to a sewer system in most urban areas and to septic tanks in less built-up areas. Sanitation has been a concern from the earliest stages of civilization. For the most part, early cities emptied their waste into rivers or seas manually or via open ditches, but emptying of chamber pots into city streets remained common into the modern era. A precursor to the modern flush toilet system was designed by John Harington in 1596 but did not become common until the late 19th century. Even London did not require indoor toilets in its building codes until after the WWI. Illustration appeared in "Metamporphosis of Ajax; a cloacinean satire" by John Harington, 16th century.